Which volcano type is typically characterized by steep sides and explosive eruptions due to high-viscosity magma?

Which volcano type is typically characterized by steep sides and explosive eruptions due to high-viscosity magma?

• A. Stratovolcanoes
• B. Shield volcanoes
• C. Volcanic cones
• D. Calderas

Answer: (A)

Magma with high silica content is thick and sticky, so it doesn’t flow far. This high-viscosity magma traps gases, building up pressure until an explosive eruption blasts ash, pumice, and volcanic bombs into the air. The eruptions throw material that falls back as layers, creating a tall, steep-sided cone as successive layers of lava and tephra pile up. This combination of steep slopes and violent, explosive activity is a hallmark of stratovolcanoes. In contrast, shield volcanoes form from low-viscosity lava that flows easily and spreads out, making broad, gentle slopes with mainly lava-flow eruptions; calderas are large collapsed basins after huge eruptions, and volcanic cones is a broader term that doesn’t specify the explosive, high-viscosity behavior.